1. Field of the Invention
The present invention relates to a display device for use in AV (audio-visual) apparatus, OA (office automation) apparatus, computers or the like, more particularly to its transmission circuit and its transmission method.
2. Description of the Related Art
Flat displays which display images on a principle different from the counterpart of CRT displays are widely applied on the market of word processors and personal computers. Development is under way to apply such flat displays to high-quality television sets and high performance EWS (engineering work stations).
Examples of typical flat displays include ELP's (electroluminescence panels), PDP's (plasma display panels) and LCD's (liquid crystal displays). Out of such displays, LCD's are regarded as the most promising because LCD's can be easily formed into a full-fledged color display and LCD's can well match LSI (large scale integrated) circuits as compared with displays of other kinds.
LCD's are roughly available in two types, a simple matrix driving LCD and an active matrix driving LCD, depending on the driving method.
Simple matrix driving LCD's comprise a pair of glass plates, stripe-like electrodes formed on the pair of glass substrates and a liquid crystal being disposed therebetween, the pair of glass plates being located opposite to each other so that the stripe-like electrodes formed on glass plates run at right angle to each other, whereby the LCD displays images with an sensitive display properties inherent in liquid crystals.
On the other hand, active matrix driving LCD's are constituted so that non-linear elements are added to pixels and images are displayed with switching properties inherent in each of the elements. Consequently, the active matrix type LCD's less depend on the sensitive display properties of the liquid crystals than the simple matrix driving type LCD's thereby realizing a display having a high contrast and being capable of quick response.
The non-linear elements are available in two types; two terminal elements and three terminal elements. Examples of two terminal non-linear elements include MIM's (metal-insulator-metal) and diodes. On the other hand, three terminal non-linear elements include a-SiTFT's (amorphous silicon thin film transistors) and p-SiTFT's (polysilicon thin film transistors).
However, large scale liquid crystal displays provide long wirings so that a wiring resistance R rises, a signal delay generated by the connection of the wiring resistance R and a parasitic capacitance (floating capacitance) C becomes larger which aggravates the uniformity of the display and a high contrast thereof. To avoid such drawback, an attempt has been made to analyze configurations of display pulses in each pixel. However, the non-linear properties of elements cause much difficulty to the theoretical analysis of the configuration, so computers are used for simulating the configuration of the display pulses.
In this manner, active matrix driving LCD's have drawbacks such as a contrast deterioration, residual images and a shortened panel life because of the presence of the parasitic capacitance between the non-linear element and the scanning line. Consequently, longer wiring length resulting from an increase in the size of displays further raises the wiring resistance R thereby providing further prolonged signal delay generated by the connection of the wiring resistance R and the parasitic capacitance C which is likely to further aggravate the uniformity in display and to impede the improvement in the display contrast.
Such phenomenon can be detailed with respect to an RC ladder-type circuit shown in FIG.7. In simple matrix driving displays and active matrix driving displays, there exists a resistance R held by a signal line and a capacitance C generated either between signal lines or between the non-linear element and a common electrode. In such case, a circuit equation relative to a current In flowing through an nth node 3 shown in FIG. 7 is represented as follows. EQU RIn=Vn-Vn+1 EQU dQn/dt=In-1-In
Here, Symbol Vn designates a voltage at the nth node, Q an amount of electric load accumulated in the nth capacitance C.
Hence, when the current is reduced, the following equation is given. EQU RdQn/dt=Vn-1-2Vn+Vn+1
When the left side of the above equation is approximated to a linear form (Q=CV) and the right side is converted into a differential form, the following diffusion equation is given. EQU RC/.DELTA..sup.2 .differential.V/.differential.t=.differential..sup.2 V/.differential.X.sup.2
where symbol .DELTA. designates a distance between two nodes of the network.
This shows that the square-shaped waveform of the voltage applied to this circuit is deformed into a configuration broading toward the bottom thereof while diffusing on a signal line. The non-linear properties of the element cause difficulties to the analysis of the configuration of the display pulses in each pixel. Computer simulation, thus, has been used. Consequently, it has been desired that an epoch-making new technology appear that can realize a uniform and a large-size and large-capacity display by overcoming the above difficulties.
To overcome such problem, a display signal of solitons may possibly be used as means of communicating image display signals to pixels. Solitons change a mode of propagating display signals from a propagation through diffusion to a propagation through wave motion with minimum signal delay and deformation of waveforms of the display signals in the transmission channel.
Solitons were found in 1965 as a wave that can be described in K-dV (Korteweg-de Vries) equation. The equation includes both non-linear items and diffused items. Solitons can be formed by a balance between a projection of waves caused by non-linear items and an expansion of waves caused by diffused items. Solitons are characterized by the fact that they never collapse even after mutual overtaking and mutual collision. The name "soliton" comes from the very fact that it behaves like a particle while maintaining its size before and after mutual collision.
The transmission circuit of solitons comprises a nonlinear LC ladder-type circuit network. The capacitance of the circuit network is generated by the junction of diodes or FET's (Field Effect Transistors) used in the switching of pixels or between the transmission channel and ground electrode. Inductors can be composed of coils, but using such inductors enlarges the whole circuit.
In addition, the relation between the pulse height and pulse width in solitons is set to a definite value. Propagating a signal having a wide pulse width requires heightening the pulse height. Consequently, driving the display at a low voltage requires using a multi-solitons solution, but the multi-solitons solution similar in the form of square-shaped pulses generates a superfluous vibrations which are not appropriate to be used as a display signal.
Incidentally, as a known device using an LC ladder-type circuit, Japanese Published Patent No. SHO 56-29224 describes a frequency selection and display apparatus comprising tuners having different tuning frequencies, the tuners being constituted so that an inductance and capacitance of tuners prevent the attenuation of information and the deterioration thereof in the direction of propagation, and the response scope of frequencies is extremely widened, the tuners selectively generating either electric and mechanical vibrations so that the display device connected to the outside converts frequencies included in information into a visible form with a liquid crystal.